Fructose stimulates the phosphorylation of glucose in the liver. The mechanism of this effect involves a regulatory protein, which, in the presence of fructose 6-phosphate, binds to, and inhibits glucokinase. Fructose gives rise to fructose 1-phosphate, which binds to the regulatory protein and causes its dissociation from glucokinase, thus allowing this enzyme to be fully active. Because of this effect, fructose can play the role of a signal which tells the liver that glucose is absorbed from the gut.